7 Quality of service (QoS) All traffic in your network receives equal priority. Noncritical browser traffic is considered as important as critical business applications. If your chief executive officer (CEO) is giving a presentation using an audio/video application, IP packet priority becomes a concern. It is critical that, during the presentation, this application receive greater performance than other applications. QoS is a new function that allows you to request network priority and bandwidth for TCP/IP applications. Packet priority is important to you if you send applications that need predictable and reliable results, such as multimedia. It is important to understand QoS before you start planning for policy rules. The following links provide you with the information you need to implement QoS. Print this topic Print this entire topic. QoS scenarios View some QoS policy scenarios to see why and how you can use QoS. QoS concepts If you are new to quality of service, view some basic QoS concepts and mechanisms. This will give you an overview of how QoS works and how QoS mechanisms work together. Planning QoS Links you to a planning advisor and network information you will need to know in order to use QoS effectively. Configuring QoS Follow these procedures to create new differentiated service policies and integrated service policies. Managing QoS Follow these procedures to edit your existing policies. These articles tell you where to find actual tasks for deleting, tracing, and using other policy management techniques. Troubleshooting QoS Use this troubleshooting section to help you debug a QoS problem. Other information about QoS Find links to other useful QoS sources. There are many other books, Web sites, request for comments (RFCs) and white papers. For additional IBM TCP/IP resources, see V4 TCP/IP More Cool things than ever or TCP/IP Tutorial and Technical Overview within the TCP/IP Redbooks topic of the Information Center. Print this topic To view or download the PDF version, select Quality of service (about 294 KB or 43 pages). To save a PDF on your workstation for viewing or printing: 1. Open the PDF in your browser (click the link above). 2. In the menu of your browser, click File. 3. Click Save As Navigate to the directory in which you would like to save the PDF. 5. Click Save. Copyright IBM Corp

8 If you need Adobe Acrobat Reader to view or print these PDFs, you can download a copy from the Adobe Web site. QoS scenarios One of the best ways to learn about quality of service is to see how the function works in your overall network picture. The following basic examples show why you would use quality of service policies. Scenario: Limit browser traffic You can use QoS to control traffic performance. Use a differentiated services policy to either limit or extend an application s performance within your network. Scenario: Dedicated delivery (IP telephony) If you need dedicated delivery and want to request a reservation, you use an integrated services policy. There are two types of integrated services policies to create: Guaranteed and controlled load. In this example, we use guaranteed service. Scenario: Predictable B2B traffic If you need predictable delivery and still need to request a reservation, you also use an integrated services policy. However, this example uses a controlled load service. Scenario: Secure and predictable results (VPN and QoS) If you are using a virtual private network (VPN), you can still create quality of service policies. This example shows the two being used together. The IP addresses and diagrams are fictitious and only used for example purposes. Scenario: Limit browser traffic Problem Your company has been experiencing high levels of browser traffic from the user-centered design (UCD) group on Fridays. This traffic has been interfering with the accounting department, which also needs good performance from their accounting applications on Fridays. You decide to limit browser traffic to the UCD group. The following figure illustrates the network setup in this scenario. Your iseries server is running on OS/400 V5R1. Figure 1. Web server limiting browser traffic to a client. 2 iseries: Quality of service

9 Solution To limit browser traffic out of your network, you could create a differentiated service policy. A differentiated service policy divides your traffic into classes. All traffic within this policy is assigned a codepoint. This codepoint tells routers how to treat the traffic. In this scenario, the policy would be assigned a low codepoint value to affect how the network prioritizes browser traffic. Configuration 1. Create the differentiated service policy. Since you want to limit browser traffic to the user-centered design (UCD) group, you might call the policy UCD. The clients use a subnet address of This is a fictitious number used for example purposes only. Web traffic generally runs on port 80, so you could name the application Quality of service (QoS) 3

10 port 80. Since the congestion only occurs on Fridays, you could apply a 9:00 AM-5:00 PM schedule to the policy. You could name this Friday9-5. Use the following settings throughout the wizard: Name = UCD (can be any name you assign) Client = Subnet Application = port 80 (well-known port for HTTP traffic) Protocol=TCP Schedule=Fridays9-5 Operations Navigator lists all the differentiated service policies created on your server. After you complete the wizard, your policy appears as follows. Figure 2. QoS Server Configuration dialog. 2. Complete a new class of service. While completing the wizard, you are asked to assign a per-hop behavior, performance limits, and out-of-profiling traffic handling. This is defined in a class of service. 4 iseries: Quality of service

11 Classes of service actually determine the performance levels that this traffic receives from a router. The following figure shows what your output would look like in Operations Navigator. You could name your class of service Bronze, to show that this traffic receives a lower service. Operations Navigator lists all the classes of service defined on your server. Figure 3. QoS Server Configuration dialog displaying your class of service selection. 3. Change any values that do not apply to this policy. After you create a class of service, you can modify any of the values you previously selected. Right-click on the class of service name shown in the preceding figure. When you select Properties, the following CoS Properties dialog appears with the values that control your traffic. Figure 4. CoS Properties dialog displaying your traffic management limits. Quality of service (QoS) 5

12 4. Use the monitor to verify your policies are working. To verify that the policy is behaving as you configured in the policy, use the monitor. Below is a dialog of the monitor output with comments to help explain the results. Figure 5. Quality of Service Monitor. 6 iseries: Quality of service

13 The most interesting fields are the fields that obtain their data from your traffic. Make sure to check the total bytes, bytes in-profile, and packets in-profile fields. Bytes out-of-profile would indicate when traffic exceeds the configured policy values. In a differentiated service policy, the out-of-profile number indicates the number of bytes being dropped. The in-profile packets indicate the number of bytes controlled by this policy (from the time the packet was started to the present monitor output). What values you assign the average rate limit field is also important. When packets exceed this limit, the server will begin to drop them. As a result, the bytes out-of-profile will increase. This shows you that the policy is behaving as you configured it to behave. See the monitoring section for a description of all the monitor fields. Scenario: Dedicated delivery (IP telephony) Problem The chief executive officer (CEO) of your company is going to give a live broadcast to a client across the country between 1:00PM-2:00PM. You must guarantee that IP telephony will have guaranteed bandwidth so there are no interruptions during the broadcast. In this scenario, the application resides on the server. The following figure illustrates the network setup in this scenario. Your iseries server is running on OS/400 V5R1. Figure 6. CEO to client presentation guaranteed by an integrated services policy. Quality of service (QoS) 7

14 Solution Extremely sensitive applications require a guaranteed connection. Since the application your CEO is using requires a smooth, uninterrupted transfer, you decide to use a guaranteed integrated services policy. Guaranteed service controls the maximum queuing delay, so that packets will not be delayed over a certain amount of time. Since you want to guarantee this connection, you could use an integrated services policy with guaranteed service. Integrated service policies require RSVP-enabled applications. In V5R1, there are no RSVP-enabled applications on the server. An application can be RSVP-enabled using the Resource Reservation Setup Protocol (RAPI) API. Integrated service policies also require that along the traffic s path, the routers are RSVP-enabled. See the Integrated service concept section for more information. Configuration 1. Create the integrated service policy. 8 iseries: Quality of service

15 Your first step is to complete the new integrated service policy wizard. Since you want to guarantee traffic from the chief executive officer (CEO), you might call the policy CEO_presentation. A single client is receiving this presentation at IP address This is a fictitious number used for example purposes only. You could name this client, Branch1. Since this traffic runs on port 2427, you could name the application port You could name the schedule 1:00-2:00. Use the following values throughout the wizard: Name = CEO_presentation Client = Branch1 Application = port 2427 (if this is the port that IP telephony is running across) Protocol=TCP Schedule=1:00-2:00 Operations Navigator lists all the integrated service policies created on your server. After you complete the wizard, your policy will appear as follows. Figure 7. QoS Server Configuration dialog 2. Change any values that do not apply to this policy. After you create this policy, you can modify the values you previously created with the wizard. Right-click on the policy name shown in the preceding screen. When you select Properties, the IntServ_Guaranteed Properties dialog appears. Select the flow control tab to change the values that control your traffic s flow. As you can see, this is also where you can edit the schedule, client, applications, and traffic management. Figure 8. IntServ_Guaranteed Properties dialog displaying your flow control limits. Quality of service (QoS) 9

16 3. Use the monitor to verify your policies are working. Below is a dialog of the monitor output with comments to help explain the results. Figure 9. Quality of Service Monitor. 10 iseries: Quality of service

17 Again, the most interesting fields are the fields that obtain their data from your traffic. These fields include the total bytes, bytes in-profile, and packets in-profile fields. Bytes out-of-profile would indicate that other traffic is getting delayed or dropped to satisfy this integrated service policy requirements. See the monitoring section for a description of all the monitor fields. Scenario: Predictable B2B traffic Problem The Sales department reports problems that network traffic is not performing as they expected. Your company s iseries server resides in a business-to-business (B2B) environment that requires predictable e-business service. You need to provide predictable transactions to your customers. You want to give the sales unit a higher quality of service for their ordering application during the busiest time of the day (between 10 AM and 4 PM). In the illustration below, you sales team is within your private network. There are RSVP-enabled routers along the traffic s path to the B2B client. Each R represents a router along the traffic s path. Figure 10. Integrated services policy to a B2B client using RSVP-enabled routers. Solution Controlled load service supports applications that are highly sensitive to congested networks, but are tolerant to small amounts of loss and delay. If an application uses the controlled load service, its performance will not suffer as network load increases. Traffic will be provided with service resembling normal traffic in a network under light conditions. Since this particular application is tolerant to some delay, you decide to use an integrated services policy using a controlled load service. Quality of service (QoS) 11

18 Integrated service policies require RSVP-enabled applications. In V5R1, there are no RSVP-enabled applications on the server. You can enable an application using the Resource Reservation Setup Protocol (RAPI) APIs. Integrated service policies also require that along the traffic s path, the routers are also RSVP-enabled. See the Integrated services concept section for more information. Configuration 1. Create a new integrated service policy. Since you want to give predictable traffic to your customers, you might call the policy B2B_CL. A single client is receiving this presentation at IP address This is a fictitious number used for example purposes only. Since this traffic runs on various ports between 7000 and 8000, you could name the application port Since this presentation is occurring from 10:00-4:00, you could name the schedule Primetime. Use the following settings throughout the wizard: Name = B2B_CL Client = Application = port Protocol=TCP Schedule=Primetime Operations Navigator lists all the integrated services policies created on your server. After you complete the wizard, your policy will appear as follows. Figure 11. QoS Server Configuration dialog. 12 iseries: Quality of service

19 2. Change any values that do not apply to this policy. After you create this policy, you can modify the values that you previously set through the wizard. Right-click on the policy name shown in the preceding figure. When you select Properties, the following dialog displays. Select the Flow control tab to change the values that control your traffic s flow. As you can see, this is also where you can edit the schedule, client, applications, and traffic management. Figure 12. Properties dialog displaying your flow control limits. 3. Use the monitor to verify your policies are working. To verify that the policy is operating correctly, use the monitor. Below is a dialog of the monitor output with comments to help explain the results. Figure 13. Quality of Service Monitor. Quality of service (QoS) 13

20 Again, the most interesting fields are the fields that obtain their data from your traffic. Make sure to check the total bytes, bytes in-profile, and packets in-profile fields. Bytes out-of-profile would indicate that other traffic is getting delayed or dropped to satisfy this integrated services policy requirements. For a full description of the monitor fields, see the monitoring section. Scenario: Secure and predictable results (VPN and QoS) Problem You have a business partner connected through a VPN and you want to combine VPN and QoS to provide security and predictable e-business flow for mission-critical data. The QoS configuration only travels in one direction. Therefore, if you have an audio/video application, you need to establish QoS for the application on both sides of the connection. The illustration shows your server and your client in a host-to-host VPN connection. Each R represents differentiated service-enabled routers along the traffic s pathway. As you can see, QoS policies only flow in one direction. Figure 14. Host-to-host VPN connection using a QoS differentiated service policy. 14 iseries: Quality of service

21 Solution You would use VPN and QoS to establish not only protection, but priority for this connection. First, you would need to set up a host-to-host VPN connection. See the Host-to-Host VPN connection example, to assist you with the VPN configuration. Once you have the protection of your VPN connection, you can set up your QoS policy. You could create a differentiated service policy. This policy would be assigned a high expedited forwarding codepoint value to affect how the network prioritizes mission-critical traffic. Configuration 1. Create the differentiated service policy. Since you want to increase performance for B2B applications, you might call the policy B2B. The clients have a single address of This is a fictitious number used for example purposes only. Since B2B traffic can use any port, you could name the application All ports. Since the congestion only occurs between 9:00 AM and 5:00 PM, we could apply a 9-5 schedule to the policy. You could name this Firstshift. Use the following settings throughout the wizard: Quality of service (QoS) 15

22 Name = B2B Client = VPNClient Application = All port Protocol=All Schedule=Firstshift Operations Navigator lists all the differentiated service policies created on your server. After you complete the wizard, your policy will appear as seen below. Figure 15. QoS Server Configuration dialog. 2. Complete a new class of service. While completing the wizard, you will be asked to assign a class of service. The class of service assigns performance limits, codepoints, and out-of-profile handling characteristics. In this policy, you will want to assign a high priority, expedited forwarding codepoint. Since you want to apply an expedited forwarding codepoint, you could name the class of service EF_VPN to remind yourself why you selected this value. The following figure shows what your output would look like in Operations Navigator. Figure 16. QoS Server Configuration dialog displaying your class of service selection. 16 iseries: Quality of service

23 3. Change any values that do not apply to this policy. You can also edit the class of service after you create it. Right-click on the name of the class of service in the dialog listed above. Select Properties and the dialog will appear with controls that manage how the IP traffic is handled. Figure 17. CoS Properties dialog displaying your traffic management limits. Quality of service (QoS) 17

24 4. Use the monitor to verify your policies are working. To verify that the policy is behaving as you configured it to behave, use the monitor. Below is a figure of the monitor output with comments to help explain the results. Figure 18. Quality of Service Monitor. 18 iseries: Quality of service

25 Similar to example 1, the most interesting fields are the fields that obtain their data from your traffic. These fields include the total bytes, bytes in-profile, and packets in-profile fields. Bytes out-of-profile would indicate when traffic exceeds the configured policy values. The in-profile packets indicate the number of packets controlled by this policy. What values you assign the average rate limit field is very important. When packets exceed this limit, the server will begin to drop them. As a result, the bytes out-of-profile will increase. The difference between this policy and the example 1 is that the packets here are protected using the VPN protocols. As you can see, QoS does work with a VPN connection. See the monitoring section for a description of all the monitor fields. QoS concepts Quality of service (QoS) terms can be found in multiple sources, so this topic will only cover the basics as they specifically apply to your iseries server. One of the most important parts of implementing quality of service is your server itself. Not only do you need to understand the concepts below, but you also need to be aware of the role your server plays in implementing these concepts. The iseries server can only act as a client or a server, not a router. You need to take this into consideration as you learn more about the concepts below and begin planning for quality of service. To implement QoS, you create policies for your traffic. The main policies are called integrated services and differentiated services. These are two distinct implementations of QoS. To decide which policy you need to use, evaluate the reason why you want to use QoS. Research the concepts below to find out what situations would be suited for an integrated services policy versus a differentiated services policy. As you research, you will discover there are times you should use a combination of the two policies called integrated services using differentiated services markings. Quality of service (QoS) 19

26 Use the following links for more information: Differentiated services This is the first type of policy you can create on your server. Differentiated services is the portion of QoS that divides your traffic into classes. To implement quality of service in your network, you need to determine how you want to classify your network traffic and how to handle the different classes. Then you can create the classes of service to use with your differentiated services policy. Differentiated classes of service Differentiated services divides your traffic using classes of service. This subtopic explains the parts that make up a class of service. When you create a differentiated services policy, you also have to create a class of service. Traffic conditioners In order for differentiated services policies to be effective, you must have routers that can handle traffic conditioners. Traffic conditioners make your routers and switches differentiated services-enabled. Integrated services The second type of policy you can create is an integrated services policy. Integrated services provides the capability for IP applications to request and reserve bandwidth using the RSVP protocol. When you create an integrated services policy, you can use a guaranteed service or a controlled load service. Integrated services using differentiated services markings This type of policy is generally used when an integrated services policy may cross a mixed network environment. A mixed network environment contains some network nodes that are RSVP-enabled and some that are not RSVP-enabled. RSVP This is the protocol that is used to make an integrated services reservation. It discusses what makes a router RSVP-enabled. Before attempting to implement QoS, you should research quality of service in depth and make sure this service will meet your needs. See the other information about QoS page for help on finding additional resources. Differentiated services Differentiated services divides your traffic into classes. To implement quality of service in your network, you need to determine how you want to classify your network traffic and how to handle the different classes. The server uses bits in the IP header to identify an IP packet s level of service. Routers and switches allocate their resources based on the per-hop behavior (PHB) information in the IP header s TOS field. The TOS field was redefined in request for comment (RFC) 1349 and OS/400 V5R1. A PHB is the forwarding behavior a packet receives at a network node. It is represented by a hexadecimal value known as a codepoint. Packets can be marked at either the server or other parts of the network, such as a router. For a packet to retain the service requested, every network node must be differentiated services-enabled. That is, the equipment must be able to enforce per-hop behaviors. To enforce PHB treatment, the network node must be able to use queue scheduling and outbound priority management. See the Traffic conditioners page for more information on what it means to be differentiated services-enabled. If your packet passes through a router or switch that is not differentiated services-enabled, it will lose its level of service. Note that the packet is still handled, but it may experience unexpected delivery. On your iseries server you can use the standard PHB codepoints or you may define your own class. It is not recommended that you create your own codepoints for use outside your private network. Unlike integrated services, differentiated services traffic does not require a reservation or per-flow treatment. All traffic placed in the same class is treated equally. 20 iseries: Quality of service

27 Differentiated services is also used for traffic control into or out of a server. This means that your iseries server really uses differentiated services to limit performance. Limiting a less-critical application allows a mission-critical application to exit your private network first. When you create a policy, you are asked to set various limits on your server. The limits include token bucket size, peak rate limit, and average rate limit. The help topics within the QoS function of Operations Navigator gives you more specific information on these limits. Now, you know a little more about using differentiated services to group your traffic. If you do not know which codepoints to assign, review codepoints and per-hop behaviors. If you still do not know which codepoints to use, use trial and error. Create test policies, monitor these policies, and make adjustments accordingly. Differentiated classes of service The differentiated services section discusses how the differentiated services function groups your traffic into classes. Even though most of this happens through equipment, you control how you group traffic and what priority the traffic should receive. As you implement QoS, you will first define policies. The policies determine the who, what, where, and when. Then you must assign a class of service to your policy. When you create a policy, you select a class of service that this policy will enforce. Classes of service are defined separately and may be reused by policies. A class of service is comprised of a per-hop behavior, traffic limits, and out-of-profile handling in the class of service. Per-hop behaviors Quality of service uses the recommended codepoints to assign per-hop behaviors to traffic. Routers and switches use these codepoints to give traffic priority levels. Your server can not use these codepoints, since it does not act as a router. You should determine which codepoints to use based on your individual network needs. Consider what applications are most important to you and what policies should be assigned higher priority. The most important thing is to be consistent with your markings, so that you get the results you expect. These codepoints will be a key part of differentiating different classes of traffic. Performance limits Quality of service uses performance limits to restrict traffic through your network. These limits are placed by setting the token bucket size, peak rate limit, and average rate limit. See the QoS help topic, Token Bucket and Bandwidth limit, within Operations Navigator for more information about these specific values. Out-of-profile handling The final portion of a class of service is out-of-profile handling. When you assign the performance limits above, you set values to restrict traffic. When traffic exceeds these restrictions, the packets are considered out-of-profile. This information in a class of service tells the server whether to drop, shape, or retransmit these out-of-profile packets. If you decide to drop out-of-profile packets, they are retransmitted after a specified amount of time. If you delay the out-of-profile packets, they are shaped to conform to your defined handling characteristics. If you remark out-of-profile packets with a Differentiated Service CodePoint (DSCP), they are reassigned a new codepoint. When you assign these handling instructions in the wizard, click Help for more specific information. Codepoints and per-hop behaviors Quality of service uses the following recommended codepoints to assign per-hop behaviors to traffic. You should determine which codepoints to use based on your individual network needs. Only you can decide what codepoint schemes make sense for your environment. You need to consider what applications are most important to you and what policies should be assigned higher priority. The most important thing is to be consistent with your markings, so that you get the results you expect. Quality of service (QoS) 21

28 This table displays the recommended codepoints. You may also create your own per-hop behaviors. Expedited forwarding (See 22) Class selector (See 22) Assured forwarding (See 22) Class Assured forwarding, Class 1, Low Class Assured forwarding, Class 1, Medium Class Assured forwarding, Class 1, High Class Assured forwarding, Class 2, Low Class Assured forwarding, Class 2, Medium Class Assured forwarding, Class 2, High Class Assured forwarding, Class 3, Low Class Assured forwarding, Class 3, Medium Assured forwarding, Class 3, High Assured forwarding, Class 4, Low Assured forwarding, Class 4, Medium Assured forwarding, Class 4, High Expedited forwarding Expedited forwarding is one type of differentiated services per-hop behavior. It is mainly used to provide guaranteed service across a network. Expedited forwarding gives traffic a low-loss, low-jitter, end-to-end service by guaranteeing bandwidth across networks. The reservation is made before the packet is sent. The main goal is to avoid delay and deliver the packet on a timely basis. Note: There is usually a high cost to receive expedited forwarding treatment, so it is not recommended to use this per-hop behavior on a regular basis. Class selector Class selector codepoints are another type of differentiated services behavior. There are seven classes. Class 0 gives packets the lowest priority and Class 7 gives packets the highest priority within the class selector codepoint values. This is the most common group of per-hop behaviors, because most routers already use similar codepoints. Assured forwarding Assured forwarding is divided into four per-hop behavior classes, which each have drop precedence levels of low, medium, or high. A drop precedence level determines how likely it is for the packets to be dropped. The classes each have their own bandwidth specifications. Class 1, High gives the policy the lowest priority and Class 4, Low gives policies the highest priority. A low drop level means the packets in this policy have the lowest chance of being dropped in this particular class level. Traffic conditioners Network equipment needs to be QoS-aware. This means that network equipment, such as routers and switches must have the following capabilities: classifiers, meters, markers, shapers, and droppers. The collection of these terms is referred to as traffic conditioners. If the network equipment has all the traffic conditioners, then it is considered QoS-aware. The following figure shows a logical representation of how traffic conditioners work: Figure 19. Traffic conditioners 22 iseries: Quality of service

29 The following information describes each of the traffic conditioners in more detail. Classifiers Packet classifiers select packets in a traffic stream based on the content in its IP header. The iseries server defines two types of classifiers. The BA (Behavior aggregate) classifies packets based exclusively on the differentiated services codepoint. The MF (Multi-field) classifier selects packets based on the value of a combination of one or more header fields, such as source address, destination address, differentiated services field, protocol ID, source port, and destination port numbers. Meters Traffic meters measure whether or not the IP packets, being forwarded by the classifier, are corresponding to the traffic s IP header profile. The information in the IP header is determined by the values you set in the QoS policy for this traffic. A meter passes information to other conditioning functions to trigger an action. The action is triggered for each packet whether it is in-profile or out-of-profile. Markers Packet markers set the differentiated services (DS) field. They take the differentiated services codepoint setting and transfer it into bytes. The marker can be configured to mark all packets to a single codepoint or to a set of codepoints used to select a per-hop behavior. Shapers Shapers delay some or all of the packets in a traffic stream to bring the stream into compliance with the traffic profile. A shaper has a finite buffer size, and packets may be discarded if there is not enough space to hold the delayed packets. Droppers Droppers discard some or all of the packets in a traffic stream. This occurs to bring the stream into compliance with the traffic profile. Integrated services Integrated services deals with traffic delivery time and assigning particular traffic special handling instructions. It is important to be conservative with your integrated services policies because it is still relatively expensive to guarantee data transfer. However, overprovisioning your resources can be even more expensive. Integrated services reserves resources for a particular policy before the data is sent. The routers are signaled before data transfer and the network actually agrees to and manages data transfer based on a policy. A policy is a set of rules that designate an action. It basically states that client, application, and schedule (which you designate) should receive a particular service. The reservation is performed using the Resource ReSerVation Protocol (RSVP) and RAPI APIs. Quality of service (QoS) 23

30 Every node that your traffic travels through must have the ability to use the RSVP protocol. The routers provide quality of service through the following traffic control functions: packet scheduler, packet classifier, and admission control. The ability to carry out this traffic control is often referred to as QoS-enabled or RSVP-enabled. As a result, the most important part of implementing integrated services policies is being able to control and predict the resources in your network. To get predictable results, every node in the network should be able to handle and enforce traffic control characteristics. For example, your traffic is routed based on resources, not on which paths have RSVP-aware routers. Crossing routers that are not RSVP-aware may cause unpredictable performance problems. The connection is still made, but the performance that the application requests is not granted. The following figure shows how the integrated service function logically works. Figure 20. RSVP path between client and server. The RSVP-enabled application on the server detects a connection request from the client. In response, the server s application issues a path command to the client. This command is issued using the RAPI APIs and contains router IP address information. A path command contains information about the available resources on the server and the routers along the path, as well as, route information between the server and the client. The RSVP-enabled application on the client then ends another command to reserve a connection to the server. This command makes the reservation based on the router information from the path command. All nodes in the pathway need to agree to the reservation. The server and all routers in the path accept the reservation. The resources requested by the application are then reserved in routers along the path, between the server and client. The server then starts transmitting data to the client. The server and all routers in the path accept the reservation. The resources requested by the application are 24 iseries: Quality of service

31 then reserved in routers along the path, between the server and client. The data is transmitted along the same route as the reservation. Again, this shows how important the routers abilities to carry out this reservation are to the success of your policies. Integrated services is not meant for short term RSVP connections, like HTTP. Of course this is at your discretion. Only you can decide what is best for your network. Consider what areas and applications are having performance problems and need quality of service. Whichever applications you use in an integrated services policy must be able to use the RSVP protocol. Currently, your server does not have any RSVP-enabled applications. You will need to write the application to use RSVP. See the RSVP section for more detail. As packets arrive and attempt to leave your network, your server determines whether or not it has the resources to send the packet. This acceptance is determined by the amount of space in the token bucket. You manually set the number of bytes to allow into your token bucket, any bandwidth limits, token rate limits, and the maximum number of connections your server should allow. If the incoming packets will cause the bucket to exceed its limit, the packets are considered out-of-profile. Your server can handle out-of-profile traffic in a few different ways. It can either delay, shape, retransmit, or drop the packets. If the packets will remain within the server s limits, the packets conform and are sent out. In integrated services, each connection is granted its own token bucket. In differentiated services, the whole subnet or range of clients share a token bucket. Integrated services using differentiated services markings This policy is most often used when you have a mixed environment. A mixed environment occurs when an integrated service reservation travels through different routers which don t support integrated service reservations, but do support differentiated services. Since your traffic passes through different domains, service level agreements, and equipment capabilities, you may not always get the service you intend. To help alleviate this potential problem, you can attach a differentiated services marking to your integrated services policy. In the event that a policy crosses a router that cannot use the RSVP protocol, your policy will still maintain some priority. The marking you add is called a differentiated class of service. See the differentiated classes of service and integrated services topics for more information. RSVP The resource reservation protocol (RSVP), along with the RAPI APIs perform your integrated services reservation. Every node that your traffic travels through must have the ability to use the RSVP protocol. The ability to carry out integrated services policies is often referred to as RSVP-enabled. For more information on what router functions are needed to use the RSVP protocol, see Traffic control functions. The RSVP protocol is used to create an RSVP reservation in all the network nodes along your traffic s pathway. It maintains this reservation long enough to provide your policies requested services. The reservation defines the handling and bandwidth that the data in this conversation will require. The network nodes each agree to provide the data handling defined in the reservation. RSVP is a simple protocol in that reservations are only made in one direction (from the receiver). For more complex connections, such as audio and video conferences, each sender is also a receiver. In this case, you must set up two RSVP sessions for each side. In addition to RSVP-enabled routers, you need to have RSVP-enabled applications to use integrated services. Since the iseries server does not have any RSVP-enabled applications at this time, you will need to write the applications using the RAPI API. This will enable the applications to use the RSVP protocol. If you want an in-depth explanation, there are many sources that explain this model, its operation, and messaging. See the other information about QoS page, for some alternative resources. Quality of service (QoS) 25

32 Traffic control functions Traffic control function only applies to integrated services policies. To get predictable results, you need to have RSVP-enabled hardware along the traffic s path. Routers must have certain traffic control functions in order to use the RSVP protocol. This is often referred to as being RSVP-enabled or QoS-enabled. Remember that, in V5R1, your server s role is either a client or a server. It can not be used as a router at this time. Traffic control functions include the following: Packet scheduler The packet scheduler manages the packet forwarding based on the information in the IP header. The packet scheduler ensures that the packet delivery corresponds to the parameters you set in your policy. The scheduler is implemented at the point where packets are queued. Packet classifier The packet classifier identifies which packets of an IP flow will receive a certain level of service based, again, on the IP header information. Each incoming packet is mapped by the classifier into a specific class. All the packets that are classified in the same class receive the same treatment. This service level is based upon the information you provided in your policy. Admission control The admission control contains the decision algorithm that a router uses to determine if there are enough routing resources to accept the requested QoS for a new flow. If there are not enough resources, the new flow is rejected. If the flow is accepted, the router assigns the packet classifier and scheduler to reserve the requested QoS. Admission control occurs in each router along the reservation path. This is not an all-inclusive discussion on classifiers and schedulers. To locate alternative sources, please review the other information about QoS page. Planning QoS The most important step to implementing quality of service is in the planning. To receive expected results, you must review your network equipment and monitor network traffic. The QoS planning advisor leads you through the basic questions you need to ask yourself during the planning phase. In addition to the advisor, consider these subtopics before implementing QoS. System requirements Lists all the requirements you need to operate QoS successfully. Ordering QoS policies The order your policies appear in the file is the order they are processed. Service level agreements Service level agreements are an important part of QoS. You must understand and set up a SLA with your network provider as part of your QoS planning. Network hardware and software Quality of service is only as good as its weakest link. The capabilities of your internal equipment and other equipment outside your network have enormous effects on QoS results. Network performance QoS is all about network performance. The main reason you are considering QoS is probably because you are already experiencing network congestion and packet loss. Before you implement any policies, you may want to use the QoS monitor to verify your IP traffic s current performance levels. These results will help you determine where congestion is occurring. See the Monitor server transactions topic under Troubleshooting. QoS planning advisor Consider these basic questions before you implement quality of service. You receive a planning worksheet with suggested policies based on your applications abilities. 26 iseries: Quality of service

33 System requirements Quality of service (QoS) is an integrated part of the operating system. Before you proceed with configuring and starting QoS, you must have the V5R1 version of OS/400. In addition, you must complete these requirements: 1. Install TCP/IP Connectivity Utilities (5722-TC1). 2. Install Operations Navigator on your PC. Make sure to install the Networking section during the Client Access install. Quality of Service is located under IP Policies within Networking. 3. Grant authority to your QoS administrator. Use the QoS task help for Granting authority to your QoS administrator in Operations Navigator. Note: If you need more information about TCP/IP, networking, or IP addresses, refer to TCP/IP Tutorial and Technical Overview and V4 TCP/IP for AS/400: More Cool Things Than Ever in the TCP/IP Redbooks topic of the Information Center. Ordering QoS policies Whenever you have two policies that overlap, the physical order of your policies on the screen in Operations Navigator is important. Overlapping policies are two policies that use the same client, application, schedules, or protocols. The policies on the Operations Navigator screen are in an ordered list. Policy precedence depends on the order of the policies in this list. However, IntServ policies are independent of DiffServ policies and vice versa. If you want one policy to take priority over another, the higher priority policy must appear in the list first. To determine if a policy overlaps with another policy, follow these instructions: 1. In iseries Operations Navigator, expand My iseries Connections (or your active environment). 2. Expand the iseries system that you are using as your central system. 3. Expand Network. 4. Double-click IP Policies. 5. Right-click Quality of Service. 6. Select Configuration. 7. Select the specific Policies folder (either IntServ or DiffServ). 8. Right-click the name of the policy that has associated overlapping policies. Overlapping policies have an icon in front of them to indicate the overlap. 9. Select Show Overlap. The overlap panel will appear. To change policy order on the screen, use the following steps once you : v Highlight the policy and use the up and down arrows on the screen to change policy order. v Right-click the policy name and select Move up or Move down. Service level agreement This section is not intended to be educational information on service level agreement (SLA) providers but points out some of the important aspects in your SLA that may affect your quality of service implementation. Your policies and reservations are only as good as the weakest link. This means, if one node anywhere between the client and the server is unable to perform any of the traffic-handling characteristics discussed in the Differentiated services or Integrated services topics, your policies will not be handled as you intended. If your SLA does not allow you enough resources, even the best policies will not help your network s congestion problem. This also involves agreements across ISPs. Across domains, every ISP must agree to support quality of service requests. Interoperability might cause some challenges. Quality of service (QoS) 27

34 Make sure that you understand the service level that you are actually receiving. Traffic conditioning agreements specifically address how traffic is handled, that is dropped, marked, shaped, or re-transmitted. The key reasons to provide quality of service involve controlling latency, jitter, bandwidth, packet loss, availability, and throughput. Your service agreements must be able to give your policies what they request. Verify that you are receiving the amount of service you need. If not, you may waste your resources. For example, if you ask to reserve 500kbps for IP telephony, but your application only needs 20kbps you may pay extra without receiving any notice from your ISP. Network hardware and software The capabilities of your internal equipment and other equipment outside your network have enormous effects on QoS results. Applications Integrated services policies require RSVP-enabled applications. Since the iseries applications are not presently RSVP-enabled, you must enable them to use the RSVP protocol. To enable your applications, you need to write special programs using the Resource Reservation Setup Protocol (RAPI) APIs. These programs will allow your applications to use RSVP. Network nodes The routers, switches, and even your own servers must have the capabilities to use quality of service. To use differentiated services policies, your equipment must be differentiated services-enabled. This means that the network node must be able to classify, meter, mark, shape, and drop IP packets. To use integrated services policies, your equipment must be RSVP-enabled. This means that the network nodes must also be able to support the RSVP protocol. For more detailed information about traffic conditioners (classify, meter, mark, shape, and drop) see the Traffic conditioners topic. For more detailed information about the RSVP protocol, see the RSVP topic. QoS planning advisor The goal of this advisor is to assist you in planning for quality of service in your network. You are asked to examine your network problem areas, applications, and equipment to determine what policies you may want to implement. This advisor does not actually create the policies for you, but produces a planning worksheet to use in the quality of service wizards. The advisor asks you to consider these questions: 1. Which users are experiencing problems in the network? 2. What clients are generating excessive network traffic? 3. What applications need limited performance, expanded performance, or predictable delivery? 4. What bandwidth characteristics and usage do your applications require? 5. Do you have the hardware and software to implement quality of service in your network? Use this link to access the QoS planning advisor. Configuring QoS You actually create your QoS policies using wizards within Operations Navigator. The wizards do an excellent job of leading your through configuration. After you configure your policies, you can use the configuration objects in Operations Navigator to edit your policy configuration. The configuration objects are the different pieces or parts that make up a policy. When you open quality of service in Operations Navigator, there are folders labeled clients, applications, schedules, policies, classes of service, and per-hop behaviors. These objects allow you to create a policy. For more detailed information about the objects, you can see the Quality of service overview help in Operations Navigator. 28 iseries: Quality of service

ERserver iseries Quality of service ERserver iseries Quality of service Copyright International Business Machines Corporation 2002. All rights reserved. US Government Users Restricted Rights Use, duplication

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